This invention relates to the treatment of heavy hydrocarbon oils and, more particularly, to an inexpensive process for reducing the viscosity of such oils.
Heavy hydrocarbon oils are typically oils which contain a large proportion, usually more than 50% by weight, of material boiling above 524.degree. C. equivalent atmospheric boiling point. Large quantities of such heavy oils are available in heavy oil deposits in Western Canada and heavy bituminous oils extracted from oil sands. Other sources of heavy hydrocarbon oils can be such materials as atmospheric tar bottoms products, vacuum tar bottoms products, heavy cycle oils, shale oils, coal-derived liquids, crude oil residua, topped crude oils, etc.
As the reserves of conventional crude oils decline, there is an increasing interest in processes for upgrading these heavy oils. However, one of the major difficulties in the processing of heavy crude oils is that they are exceedingly viscous and difficult to pump through pipelines.
Heavy oils of the above type can be considered as having both macro and micro structural properties as well as having chemical constitutive molecules. The latter are generally classified as belonging to two distinct categories, namely maltenes (soluble in 40 volumes of pentane) and as asphaltenes (soluble in toluene but insoluble in pentane). The spatial organization of maltenes and asphaltenes results in the macro and micro structural properties, with the macromolecular organization causing the high viscosities which are such a great problem in transportation of these oils. In fact, the high viscosity of heavy oils normally necessitates the addition of a diluent before they can be transported through pipelines. The costs of the diluent, the additional costs of transporting the diluent and the costs of later removing the diluent greatly increase the total cost of processing heavy hydrocarbon oils.
At the molecular level, the asphaltenes are formed by polynuclear aromatic molecules to which are attached alkyl chains. These asphaltene unit molecules are grouped in layers having several unit molecules, typically 5 or 6, surrounded by or immersed within the maltene fluid. The latter can be conveniently considered as being composed of free saturates, mono and diaromatics and resins which are believed to be associated with the asphaltenes. This organization is considered to be the microstructure and the layers of asphaltenes can be considered as a microcrystalline arrangement. The above microstructural organization forms aggregates in which several microcrystallites arrange themselves together to form a so-called micellar structure which is also known as a macrostructure. This micellar structure exhibits very strong associative and cohesive forces between the aggregates and this induces the troublesome high viscosities, since the heavy oil behaves more as a sol/gel system than as a free flowing liquid.
Normally very high processing temperatures are required to break the very strong associative forces between the micell components and such high temperatures typically result in extensive modification of the constitutive molecules, e.g. dealkylation and cracking, leading to the formation of coke precursors and, inevitably, to coke formation (toluene insoluble carbonaceous material). It is an object of the present invention to develop a simplified process which will successfully break up the micellar structure without requiring the high temperatures which cause coke formation.